JPH06106748A - Thermal head - Google Patents

Abstract

(57) [Summary] [Purpose] To miniaturize the thermal head in which the position of the heating resistor protrudes. A high surface 43 on which a heating resistor 51 is located and a low surface 47 to which a wiring member 65 is connected are formed, and a recess 49 is formed at the boundary between the inclined surface 45 and the low surface 47. It is possible to prevent the thick film 50 formed on the surface of the substrate from rising up at the boundary between the inclined surface 45 and the low surface 47, and the wiring member 65 can be satisfactorily connected to the electrodes 52 and 53 in this vicinity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head such as a thermal printer for printing a prepaid card or the like.

[0002]

2. Description of the Related Art At present, for example, a thermal printer for printing on a prepaid card is also used.
Therefore, as a first conventional example of a thermal head used in such a thermal printer, an apparatus disclosed in Japanese Patent Laid-Open No. 1-113262 will be described with reference to FIGS. 9 and 10. First, in this thermal printer 1, as illustrated in FIG. 9, an individual electrode 4 and a common electrode 5 are provided on both ends of a glass glaze layer 3 formed on the surface of a ceramic substrate 2 which is a head substrate. Heating resistor 6 integrally formed
Are continuously provided by photolithography or the like, and the ceramic substrate 2 is attached to an end surface of a rectangular parallelepiped radiator plate 7. A driver IC (Integrated Circuit) 8 which is a drive circuit is mounted on the front surface of the heat sink 7, and the driver IC 8 is attached to the individual electrode 4 on the ceramic substrate 2 by a bonding lead 9 which is a wiring material. TA
It is connected by B (Tape Autometed Bonding). Then, these driver IC 8 and bonding lead 9
A thermal head 11 is formed by attaching a protective cover 10 covering the individual electrodes 4 and the like to the heat dissipation plate 7.

In this thermal printer 1, as shown in FIG. 10, a platen roller 12 is axially supported at a position facing the heating resistor 6 exposed from the end surface of the protective cover 10 of the thermal head 11. And
A conveyance path for the ink ribbon 13 and the recording medium 14 is formed between the platen roller 12 and the ceramic substrate 2.

In such a structure, in the thermal printer 1, the heating resistor 6 is generated by selectively switching the driver IC 8 according to the input print data.
The driving power is applied to the recording medium 14, and the recording medium 14 is conveyed by the rotation of the platen roller 12 in synchronization with the heating scanning of the heating resistor 6, so that the ink ribbon 1 is printed on the recording medium 14.
Image printing is performed by fusing the ink of No. 3.

Here, in the above-described thermal printer 1, by covering the connecting portion between the individual electrode 4 and the bonding lead 9 with the protective cover 10, it is possible to prevent the ink ribbon 13 and the recording medium 14 from coming into contact therewith. ing. But,
Since the protective cover 10 protrudes from the heating resistor 6, the recording medium 14 pressed by the platen roller 12 against the heating resistor 6 is bent at a step between the heating cover 6 and the protective cover 10, as illustrated in FIG. Will be done. That is, it is difficult for the thermal printer 1 to use a non-curvable prepaid card or the like as the recording medium 14.

As a thermal head that has solved such a problem, there is an apparatus disclosed in Japanese Patent Laid-Open No. 60-21263. Therefore, this thermal head will be described as a second conventional example with reference to FIG. In this thermal head 15, a cylindrical glass glaze layer 17 is formed on an end surface of a ceramic substrate 16, and a heating resistor 6 is formed on a flat surface of 1.0 to 2.5 (mm) located on the upper surface thereof. ing. The other structure is the same as that of the thermal printer 1 described above.

With this configuration, in the thermal head 15, even if the protective cover 10 is attached so as to cover the individual electrodes 4 and the platen roller 12 is arranged on the heating resistor 6 so as to face each other, the heating resistor 6 is also provided. Can be projected beyond the surface of the protective cover 10. Therefore, in the thermal head 15, it is possible to prevent the recording medium 14 from being bent by the platen roller 12 and pressed against the heating resistor 6, so that a non-curvable prepaid card or the like can be used as the recording medium 14. Is.

However, since the thermal head 15 needs to be formed with the heating resistor 6 by photolithography or the like so as to be located on the upper surface of the curved surface of the glass glaze layer 17, there is a problem that the productivity thereof is lowered. there were.

In order to solve the above-mentioned various problems, the thermal head of Japanese Patent Application No. 4-67994 proposed by the present applicant will be described here as a prior art of the present invention with reference to FIG. . First, in the thermal head 19 of the thermal printer 18 illustrated here, the inclined planes 22 and 23 on both sides in the sub-scanning direction of a high plane 21 projecting substantially in the center of the head substrate 20 in the sub-scanning direction in the main scanning direction. Is formed, and a low plane 24 parallel to the plane 21 is formed on one of the inclined surfaces 22 and 23. Here, the high plane 21, the inclined surfaces 22 and 23, and the low plane 24 extend in the main scanning direction of the head substrate 20, and the heating resistor 25 is provided on the plane 21 protruding from the other. The common electrode 2 is formed on the inclined surfaces 22 and 23.
6 and individual electrodes 27 are formed, and terminals 28 and 29 of the electrodes 26 and 27 are formed on the flat surface 24. Further, in the thermal head 19, the glass glaze layer 30 is formed on the flat surface 21 of the head substrate 20, and the surface other than the terminal portions 28 and 29 is shielded by the protective film 31.

The thermal printer 18 has a structure in which the thermal head 19 having the above-described structure is mounted on the end surface of the heat dissipation plate 32, and the drive circuit is arranged on the side of the heat dissipation plate 32. Further, in the thermal printer 18, the head substrate 20 protruding from the heat dissipation plate 32 is used.
An anisotropic conductive film (not shown) on the terminals 28, 29 of the
A flexible wiring material such as FPC (Flexi
ble Printed CircuiteBoard) 33 is connected,
The FPC 33 is bent at a substantially right angle, and the lower end portion is fixed to the side surface of the heat dissipation plate 32 via the circuit board 34 and the spacer 35. The FPC 3 is formed in the gap between the heat dissipation plate 32 and the FPC 33 formed in this way.
A driver IC (Integrated Circuit) 37, which is a mounting component of a drive circuit, which is die-bonded and connected by a bonding wire 36 or the like, is located on the back surface of 3.

In the thermal printer 18, the driver IC 37 mounted on the FPC 33 is potted with a sealing material 38 such as resin and the same sealing material 3 is used.
8 is applied to the side surface of the heat dissipation plate 32, and the FPC is released.
33 and the heat dissipation plate 32 are joined by the sealing material 38 to secure the strength. Further, the circuit board 34 is connected to the FPC3.
A chip component 39 such as a capacitor is mounted on the surface directly connected to the back surface of the printer 3, and a printer controller (not shown) is connected to a connection connector 40 provided on the lower edge of the chip component 39. ing.

In the thermal head 19 of the thermal printer 18 having such a structure, the flat surface 21 on which the heating resistor 25 for actually printing on the recording medium 14 is located.
Protrudes from the surfaces 22 to 24 located in front of and behind it, it is possible to convey the recording medium 14 such as a plastic card in a straight line without bending. The structure in which the heating resistor 25 of the thermal head 19 projects in this way is realized by the surfaces 21 to 24 formed continuously on the head substrate 20, and such surfaces 21 to 23.
Since it is easy to form the heating resistor 25 and the electrodes 26, 27 on the thermal printer 18, the thermal printer 18 has better productivity of the thermal head 19 than the thermal printer exemplified as the second conventional example.

In the above-mentioned application disclosing such a thermal head 19, a large-sized substrate made of alumina, ceramic or the like is ground or cut, or the green sheet before firing is ground. It is disclosed that a mass-produced substrate (not shown) of the head substrate 20 is formed by molding by die pressing, powder pressing, injection molding, or the like and then firing.

[0014]

In the above-mentioned thermal head 19, the heating resistor 25 is formed on the highest plane 21 of the head substrate 20, and the surface 22 lower than the plane 21.
By forming the electrodes 26 and 27 on 24 and connecting the FPC 33, the recording medium 14 is conveyed linearly without interference with the FPC 33 and the like to perform image printing.

Here, in the thermal head 19, as described above, the electrodes 26 and 27 are formed on the lower surfaces 22 to 24 of the head substrate 20 and the FPC 33 is connected thereto.
The quality of the connection of the FPC 33 and the pattern of the electrodes 26 and 27 depends on the smoothness of the plane 24. For this reason,
In the thermal head 19 as described above, the head substrate 20
Since the surfaces 22 to 24 of No. 2 are required to have good smoothness, their productivity is hindered.

Therefore, in order to solve the above problems, the present applicant proposes to form the glass glaze layer 30 on the surfaces 22 to 24 of the head substrate 20 as in the case of the flat surface 21 to improve the smoothness. did. However, in this case, the inclined surface 23 and the flat surface 24, which are concave and continuous to the side of the high flat surface 21, are formed.
It has been found that the glass glaze layer 30 is deposited on the boundary between and, and the glass glaze layer 30 rises at this position to hinder the connection of the FPC 33 and the patterning of the electrode 27. In particular, in such a position where the glass glaze layer 30 rises, it is difficult to satisfactorily connect the wiring material such as the FPC 33 and the bonding wire (not shown) to the terminal portions 28 and 29. Glaze layer 3
At the position away from the position where 0 rises, the terminal parts 28, 29
It is necessary to extend the head substrate 20 in the sub-scanning direction so that the head substrate 20 can be connected to the FPC 33.

The present invention is to obtain a thermal head capable of satisfactorily connecting a wiring member to an electrode in the vicinity of the boundary between an inclined surface and a low surface.

[0018]

A large number of heating resistors are continuously provided in the main scanning direction on the surface of a head substrate, and wiring members are formed on electrodes formed integrally with each of the heating resistors in the sub scanning direction. In the connected thermal head, a high surface on which the heating resistor is located and a low surface to which the wiring member is connected are formed on the head substrate, and the inclined surface and the low surface continuous to the high surface of the head substrate are formed. A recess was formed at the boundary with the surface.

[0019]

Since the thick film formed on the surface of the head substrate can be prevented from rising at the boundary between the inclined surface and the low surface,
It is possible to obtain a thermal head in which a wiring material can be satisfactorily connected to the electrode near the boundary between the inclined surface and the low surface.

[0020]

Embodiments of the present invention will be described with reference to FIGS. First, in the thermal head 41, as illustrated in FIG. 1, inclined planes 44 on both sides in the sub-scanning direction of a high flat surface 43 projecting at a substantially central position in the sub-scanning direction of an elongated head substrate 42 in the main scanning direction. 45 is formed, and low planes 46 and 47 parallel to the plane 43 are formed on both of these inclined surfaces 44 and 45. In the thermal head 41, the inclined planes 44 and 45 and the flat plane 4 that is low
6 and 47, each of which has an elongated recess 4 in the main scanning direction.
8 and 49 are formed, and the glass glaze layer 50 is formed on substantially the entire planes 43 to 47 of the head substrate 42 through the recesses 48 and 49.

A heating resistor 51 is formed on the high plane 43 through the glass glaze layer 50, a common electrode 52 is formed on the inclined surface 44, and an individual electrode 53 is formed on the inclined surface 45. Is being formed. In addition, the terminal portions 54 and 55 of the electrodes 52 and 53 are provided on the low plane 47.
The common electrode 52 on the flat surface 46 is formed with a thick film (not shown) of gold or the like for reinforcement. Further, in the thermal head 41, the terminal portion 54,
The surfaces other than 55 are shielded by a protective film 56.

As shown in FIG. 2, the thermal printer 57 using the thermal head 41 having the above-described structure includes the thermal head 41 having the above-described structure and one rigid portion 59 of the rigid FPC 58. The heat sinks 60 having an inverted L shape are arranged side by side, and the flexible portion 61 of the rigid FPC 58 is provided on the upper side surface of the heat sink 60.
The other rigid portion 62 is attached to the lower side surface of the heat radiating plate 60 so as to be positioned. Further, in the thermal printer 57, the driver IC 63 and the capacitor 6 are provided on the surfaces of the rigid portions 59 and 62 of the rigid FPC 58.
4 and other circuit components are mounted, and the driver IC 6
3 is connected to the terminal portions 54 and 55 of the thermal head 41 and the rigid portion 59 of the rigid FPC 58 by a bonding wire 65 which is a wiring material.

Further, in this thermal printer 57,
The driver IC 6 mounted on the rigid FPC 58
3 is potted with a sealing material 66 such as resin, and the sealing material 66 is shielded to flatten the flat surface 43 of the head substrate 42.
A protective cover 67 having a continuous shape is attached to the heat dissipation plate 60. In addition, in this thermal printer 57,
A connection connector 68 is mounted on the back surface of the rigid portion 62 of the rigid FPC 58.
A printer controller (not shown) is connected to the. Further, in this thermal printer 57,
A thermistor 69 is attached to the upper lower surface of the heat sink 60, and a bolt hole 70 penetrates the lower side surface of the heat sink 60. The heat sink 60 is attached to the main body of the device by a bolt (not shown) inserted in the bolt hole 70. (Not shown). Further, in this thermal printer 57, a platen roller 71 is pivotally supported at a position facing the heat generating resistor 51 of the thermal head 41, and an ink ribbon or a ribbon is provided between the platen roller 71 and the thermal head 41. A conveyance path for a recording medium (both not shown) is formed.

In the thermal head 41 of the thermal printer 57 having such a structure, the plane 43 on which the heating resistor 51 for actually printing on the recording medium is located is
Since it protrudes from the planes 44 to 47 located in front of and behind it, it is possible to convey a recording medium such as a plastic card in a straight line without bending. Then, the plane 43 in which the structure in which the heating resistor 51 of the thermal head 41 projects in this way is continuously formed on the head substrate 42.
˜47, it is easy to form the heat generating resistor 51 and the electrodes 52, 53 on the planes 43 to 47, and thus the thermal head 41 has good productivity.

Here, in this thermal head 41, the bonding wires 65 are connected by forming the electrodes 52, 53, etc. on the lower planes 44 to 47 of the head substrate 42 as described above. And the quality of the pattern of the electrodes 52 and 53 depends on the smoothness of the planes 46 and 47. Therefore, in this thermal head 41, the glass glaze layer 50 is uniformly formed on the flat surfaces 44 to 47 of the head substrate 42 to improve the smoothness thereof, thereby connecting the bonding wires 65 and connecting the electrodes 5 to each other.
Good patterning of 2,53 is achieved.

Further, when the glass glaze layer 50 is uniformly formed on the flat surfaces 43 to 47 of the head substrate 42 with the central flat surface 43 protruding as described above, the glass glaze layer 50 is formed.
Planes 44, 46 that are concave and continuous to the side of the plane 43 with high
And the planes 45 and 47 are raised at the boundary, and the connection of the bonding wire 65 and the patterning of the electrodes 52 and 53 may be disturbed. Therefore, in the thermal head 41, the planes 44 and 46 and the plane 4 as described above are used.
By forming the recesses 48, 49 at the positions of the boundaries with 5, 47, an extra glass glaze layer 50 is deposited in the recesses 48, 49 to secure the smoothness of the glass glaze layer 50 and to bond the bonding wire. 65 connection and electrodes 52, 5
The patterning of No. 3 is successfully realized. The two recesses 48 and 49 do not necessarily require both,
It is only necessary in the direction of connecting the bonding wire 65 to the terminal portions 54 and 55 of the electrodes 52 and 53.

By doing so, in this thermal head 41, it is not necessary to provide the terminals 54 and 55 on the side of the position where the glass glaze layer 50 rises, and these terminals 54 and 55 are recessed 49. Since it is possible to reduce the size of the head substrate 42 in the sub-scanning direction by providing the thermal head 41, the thermal head 41 can be reduced in size and weight.

Then, the head substrate 4 having the above-mentioned shape
As the manufacturing method of No. 2, the applicant of the present invention molds and hardens powder, mud, green sheet, etc., hardens a previously cut green sheet, and injection-molds powder and mud. Then, I proposed to bake it. Therefore, when the applicant of the present invention prototyped the head substrate 42 by various manufacturing methods as described above, it was confirmed that the manufacturing method by injection molding satisfied the shape accuracy, productivity, stability, and the like.

Further, in the manufacturing method by injection molding as described above, as shown in FIG.
By manufacturing the mass-produced substrate 72 having a shape in which 2 are connected in the sub-scanning direction, a plurality of head substrates 42 can be obtained with good productivity from the mass-produced substrate 72 formed by one injection molding. However, in the manufacturing method by such injection molding, the plate thickness of the mass-produced substrate 72 can be set to 1.5 (mm) or more in consideration of the inflow of the raw material into the mold (not shown) and the curve at the time of firing. Although desirable, this may make it difficult to cut the mass-produced substrate 72. Therefore, the applicant of the present invention is
By forming the recesses 73 and 74 at the cutting position on the back surface of 2 at the time of injection molding, the mass production substrate 7 is formed at the positions of the recesses 73 and 74.
2 is easily cut by laser scribing and the head substrate 42 is cut.
I was able to obtain.

In addition, here, the head substrate 42 is alternately reversed in the direction of continuous installation so that the planes 46 and 47 are continuous with each other, thereby simplifying the shape and facilitating resist coating and laser scribing. To be able to run. That is, when a head substrate (not shown) formed by connecting head substrates 42 arranged in the same direction is formed, the slightly lower plane 46 and the extremely lower plane 47 are not continuous, so for example, a vertical plane is formed here. In this case, the resist to be applied may be deposited and the flat surfaces 46, 47
When the gaps are made continuous by an inclined surface, the width of cutting by laser scribing increases and the mass-produced substrate as a whole also becomes large. Therefore, this mass production substrate 72 is used as the head substrate 4
2 are alternately reversed in the direction in which the flat surfaces 46 and 4 are flat.
The productivity is improved by connecting 7 to each other.

Therefore, a specific example of the method of manufacturing the head substrate 42 by such injection molding will be described in detail below. First,
Powders such as silica and calcia are put into alumina powder having a purity of 99.9 (wt%), and this is thoroughly mixed with an alumina ball mill to prepare an alumina powder having a purity of about 96 (wt%).
Next, a binder is added to the alumina powder, the mixture is thoroughly mixed, and injection molding is performed using this as a raw material with a mold having a predetermined shape to form a mass-produced substrate 72. The mass-produced substrate 72 thus formed is baked at 1400 to 1600 (° C.) after the binder removal step, and the production of the mass-produced substrate 72 is completed.

However, in the firing process as described above,
Since the mass-produced substrate 72 contracts by 15 to 25 (%), it is necessary to form an injection mold to compensate for the contraction. Therefore, the present applicant forms a plurality of types of flat plates (not shown) having various plate thicknesses by injection molding and fires them, and compares the dimensional difference between the flat plates and the mold to reduce the shrinkage. The rate and degree of deformation were investigated. First, the Applicant has determined that the thickness of the flat plate is 0.5, 1.0, 1.5, 2.0,
A mold set to 2.5 and 3.0 (mm) was prepared, and a flat plate was injection-molded so that the shrinkage rate was 15 (%) in the raw material particle size distribution and firing conditions. Then the mold gap is 0.5
Voids are generated in the flat plate of (mm) probably because the raw material does not flow in well, and it is difficult to apply it to the mass production substrate 72 because the flat plate with a mold gap of 1.0 and 1.5 (mm) is significantly deformed. It was confirmed that a flat plate having a mold gap of 2.0 (mm) or more can be applied to the mass-produced substrate 72 with little deformation. Further, when firing flat plates in such injection molding, since a plurality of flat plates are loaded and fired at once, by considering the loading method of flat plates at the time of firing and the placing method of heavy weight, etc., It has been found that even if the die gap is 1.5 (mm), the flat plate is only slightly deformed and can be applied to the mass-produced substrate 72.

Therefore, in the mass-produced substrate 72 prototyped by the applicant based on the above-mentioned data, the concave portion 7 is provided at a predetermined position in order to easily perform the laser scribing as described above.
3, 74 are formed, but as illustrated in FIG. 3, the recess 73 is not formed at a position where the plate thickness is relatively thin even at the position where the laser scribe is used for cutting. More specifically, the lowest plane 4 of the head substrate 42
No concave portion 73 is formed at a position below
The plate thickness at the cutting position is made substantially uniform by forming the recessed portion 73 at a position below 3 to 46.

Here, the applicant of the present invention has made the recess 7 as described above.
A mass-produced substrate (not shown) having a flat back surface without forming 3, 74 was first trial-produced and the deformation after firing was investigated. At this time, since the steps of the mold forming the flat surfaces 43 to 47 of the head substrate 42 are 0.3, 0.6, 0.8, 1.0 and 1.2 (mm), the minimum gap in the mold is the maximum plate thickness of the mass production substrate. It is the one obtained by subtracting the minimum step of the planes 43 to 47. Then, the maximum gap of the mold, which is the maximum thickness of the mass production substrate,
When 1.0, 1.5, 2.0, 2.5, and 3.0 (mm) were used and the shrinkage rate of the mass-produced substrates during firing was 15 (%), the results shown in Table 1 below were obtained.

[0035]

[Table 1]

In this experiment, when both the method of injecting the raw material into the mold in parallel with the unevenness and the method of injecting the material vertically were performed, the maximum gap was 1.5 (mm) or more and the minimum gap was about 1.0 ( mm) or more, it was confirmed that the deformation was within the allowable range by any injection method. Further, when the voids in the mold are substantially square, the method of injecting the raw material perpendicularly to the concavo-convex deforms more remarkably than the method of injecting parallel, and the deformation decreases as the gap in the mold increases. It was also confirmed.

Here, when actually manufacturing the thermal head 41 as a product, it is possible to increase the length in the main scanning direction corresponding to the recording medium. When it is extended in parallel, it becomes difficult to inject the raw material in parallel with the concave and convex of the mold, so that it is necessary to inject vertically. Therefore, considering the above experimental results under such conditions, in order to form a mass-produced substrate by injection molding of a ceramic containing alumina as a main component, the minimum gap of the mold is set to 1.0 (mm) or more. It will be necessary. In this case, the minimum thickness of the mass-produced substrate after firing is 0.8 (m
m) or more, and if the steps of the flat surfaces 43 to 47 are added to this, the maximum plate thickness becomes 1.1 to 1.3 (mm) or more, and it is extremely difficult to cut this by laser scribing.

Therefore, the applicant of the present invention forms the recesses 73 and 74 at the important points of the mass-produced substrate 72 as described above so that the plate thickness at the cutting position becomes 1.0 (mm) or less and the laser scribing is simplified. I was able to go to. At this time, in the mass production substrate 72 actually manufactured by the applicant, the maximum thickness after firing is set to
2.0 (mm), maximum step difference on the front side is 0.8 (mm), concave part on the back side 7
Since the maximum step of 3,74 is 1.0 (mm), the minimum gap of the mold corresponding to these values is 2.35 (mm), 1.41 (m
m) and 1.18 (mm), both of which are over the allowable value of 1.0 (mm). Then, when the raw material is injected into such a mold in parallel with the concavities and convexities, the raw material flows in perpendicular to the concave portion 73, but the mass-produced substrate 72 to be formed.
It was confirmed that there was no adverse effect on. It should be noted that such laser scribing recesses 73 and 74 are provided on the mass production substrate 7
It is also possible to form it on the surface of No. 2, but in this case, the concave portion 7 is formed in the glass glaze layer formed on the surface of the mass production substrate 72.
Since the parts 3 and 74 have an influence, the recesses 73 and 74 are formed on the back surface of the mass production substrate 72 here.

Therefore, the applicant of the present invention has made the glass glaze layer 5 only on the plane 43 of the mass-produced substrate 72 actually formed by injection molding.
0 was formed by thick film printing, and this was divided by laser scribing to form the head substrate 42. Further, here, as a comparison target, the head substrate 4 having the same shape even in the cutting of a flat plate is used.
2 was formed, and the glass glaze layer 50 was formed only on the flat surface 43. In addition, these head substrates 42
Then, as illustrated in FIG. 1, the width in the sub-scanning direction is 2.0 (mm) on the plane 43, 1.0 (mm) on the plane 44, and 3.
0 (mm), plane 46 is 2.0 (mm), plane 47 is 3.0 (mm), and the step is 0.8 (mm) between planes 43 and 47, plane 4
The distance between 3 and 47 was 0.2 (mm).

Then, the head substrate 42 having such a shape
When the heating resistor 51 made of BaRuO ₃ and the electrodes 52, 53 made of Ti—N, Al were sequentially formed on the flat surfaces 43 to 47 and patterned by photolithography, the head substrate 42 formed by injection molding showed The step is 0.8 (m
It was confirmed that disconnection frequently occurred at the position of m) or more, and the head substrate 42 formed by the cutting process had many disconnection as a whole and the yield was extremely low.

In this case, the larger the step, the more the electrodes 52, 5
It is obvious that the wire breakage is remarkable in No. 3, but since the occurrence rate of wire breakage is different in the head substrate 42 having the same shape and different molding method, it is considered that this is due to the surface roughness of the flat surfaces 43 to 47. . Therefore, when this was investigated, the surface roughness R of the planes 43 to 47 of the head substrate 42 formed by injection molding
a is 4000 to 5000 (Å) on average, whereas the surface roughness Ra of the flat surfaces 43 to 47 of the head substrate 42 formed by cutting is good at 3500 to 4000 (Å) on the high flat surface 43. However, in the low planes 46, 47, etc., it is 6000 to 10000 (Å), which is too large, and especially in the boundary positions of the planes 43-47, the inclined planes 44, 45, etc., it is several μm or more.

That is, the head substrate 4 having the above-described shape
In the case of No. 2 as well, it can be inferred that the electrodes 52, 53, etc. can be satisfactorily formed by reducing the surface roughness and improving the smoothness. However, it has been found that it is difficult to reduce the surface roughness of the head substrate 42 to an allowable value. Therefore, the applicant has formed the glass glaze layer 50 over the entire planes 43 to 47 of the head substrate 42 to improve the smoothness of the surface and form the electrodes 52 and 53 well.

Therefore, the glass glaze layer 5 having a thickness of 30, 60, 80, 100 (μm) is formed on the head substrate 42 as described above.
Results of presence / absence of disconnection when 0 is formed by the spray method and the screen printing method and the electrodes 52 and 53 are formed thereon are sequentially illustrated in Tables 2 and 3 below.

[0044]

[Table 2]

[0045]

[Table 3]

As is clear from the table above, the head substrate 4
When the glass glaze layer 50 is formed on the entire area of the surface of No. 2, the film of the glass glaze layer 50 is formed regardless of the method of forming the head substrate 42, the steps of the flat surfaces 43 to 47, and the method of forming the glass glaze layer 50. If the thickness is 30 (μm), the electrodes 52 and 53
When the film thickness is 60 (mm) or more due to disconnection in the electrodes 52, 53
Was found to be well formed. Therefore, when the surface roughness of the glass glaze layer 50 was measured, it was found that
It was confirmed to be extremely small as 300 to 800 (Å) and suitable for forming the electrodes 52 and 53.

Further, when the glass glaze layer 50 is formed on the surface of the head substrate 42 having the unevenness as described above, the glass glaze melted during the firing flows due to gravity and surface tension, so that the glass glaze 50 flows. Layer 50 is
The high plane 43 has an arc shape, and the inclined planes 44, 4
It was found that in No. 5, the raw material flows to the lower flat surfaces 46 and 47 to reduce the film thickness, and rounds are formed at the boundary positions of the respective flat surfaces 43 to 47. In particular, at the convex boundaries located on both sides of the plane 43, the radius is formed due to the increase in the film thickness of the glass glaze layer 50. Therefore, it is an essential requirement that the glass glaze layer 50 be formed well at this position. Becomes

The head substrate 42 on which the glass glaze layer 50 is formed on the entire surface as described above is closer to the boundary of the planes 43 to 47 than the head substrate 42 on which the glass glaze layer 50 is not formed. It was confirmed that the flow of the photoresist was good and the coating could be performed evenly without forming a radius by polishing or the like. Furthermore, when an aluminum film to be the electrodes 52 and 53 is formed on the head substrate 42 as described above, the glass film 5 is formed.
The head substrate 42 on which 0 is not formed has a low smoothness and thus becomes cloudy, but the head substrate 42 on which the glass glaze layer 50 is formed over the entire region has a high smoothness and thus has a mirror surface.
In this case, the reflection of the exposure light rays in the ultraviolet region becomes a problem during patterning, which is caused by forming an antireflection film on the exposure mask and making the surface of the aluminum film cloudy by changing the film forming conditions. The applicant has confirmed that the solution is simple.

Then, in the thermal head 41 actually manufactured by the present applicant, the electrodes 52 and 53 are formed on the glass glaze layer 50 of the head substrate 42 at a density of 200 (DPI; Dot Per Inch) as described above. Then, mullite having a film thickness of 5.0 (μm) and SIC having a film thickness of 3.0 (μm) were sequentially formed thereon by sputtering to form a protective film 56 having a two-layer structure.

Therefore, the applicant of the present invention adheres the thermal head 41 completed as described above and the rigid portion 59 of the rigid FPC 58 to the heat sink 60 side by side, and the driver IC 63 die-bonded on the rigid portion 59. The bonding pad (not shown) and the terminals 54 and 55 of the electrodes 52 and 53 of the thermal head 41 are connected by the bonding wire 65. At this time, the driver IC 63
Bonding pad and terminal portion 5 of the thermal head 41
4, 55 are formed on substantially the same plane so as to have the same arrangement density, and the width of the thermal head 41 in the sub-scanning direction is
The positions where the 2.7 (mm) terminal portions 54 and 55 were formed on the 3.0 (mm) flat surface 47 and the bonding wires 65 could be satisfactorily connected were examined.

Then, the bonding wire 65 is
At least from the boundary of the planes 45 and 47 of the head substrate 42
It was found that 1.0 (mm) had to be connected to the terminal portions 54 and 55 at the separated positions. That is, in the thermal head 41 prototyped at this point, the recess 49 is formed in the head substrate 42.
Since no glass is formed, the glass glaze layer 50 rises on the boundary between the flat surfaces 45 and 47, and the terminal portions 54,
It was difficult to satisfactorily connect the bonding wire 65 to 55. This means that the head substrate 42 needs to be extended in the sub-scanning direction, which impedes the reduction in size and weight of the thermal head 41.

Therefore, in order to solve the above problems, the present applicant forms the recesses 48 and 49 in the head substrate 42 to form the planes 44 and 46 and the planes 45 and 45, as illustrated in FIG. 4A. The glass glaze layer 50 was prevented from rising on the boundary with 47, and the bonding wire 65 could be satisfactorily connected to the terminal portions 54, 55 especially near the boundary between the planes 45, 47. Therefore, the applicant of the present invention has
The width and depth of the concave portion 49 of the
Table 4 below shows an experimental result assuming the distance between the boundary of No. 7 and the position where the bonding wire 65 can be connected. Here, the width and depth of the recess 49 are shown by the dimensions of the head substrate 42 after firing, and the glass glaze layer 50 is formed by screen printing.

[0053]

[Table 4]

As is clear from the table above, the head substrate 4
By forming the recess 49 at the boundary between the two flat surfaces 45 and 47, the bonding wire 65 can be satisfactorily connected even in the vicinity of this boundary, which contributes to the reduction in size and weight of the thermal head 41. In the above result, when the width of the recess 49 is 0.5 (mm) or more, the distance is slightly improved even if the depth is increased. However, as illustrated in FIG. This is because the glass glaze layer 50 sinks due to excessive size.

Next, as a first modification of the present invention, the present applicant forms the recess 75 in a stepwise shape with a wide and shallow upper portion and a narrow and deep lower portion, as illustrated in FIG. 5A. The glass glaze layer 50 was formed on the above-described head substrate 76, and the distance at which the bonding wire 65 could be connected was assumed. Therefore, the results of this experiment are illustrated in Table 5 below. In addition, here, the depth of the upper part and the lower part of the recess 75 is set to H1, H.
2, the width of the lower part is W1, and the difference in width between the upper part and the lower part is W2
And

[0056]

[Table 5]

As is apparent from the above table, by forming the stepped recess 75 as described above in the head substrate 76,
Further, the position where the bonding wire 65 can be connected is brought close to the boundary between the planes 45 and 47 of the head substrate 76, which can contribute to the reduction in size and weight of the thermal head (not shown).

Further, as a second modified example of the present invention, the applicant of the present invention, as shown in FIG.
A similar experiment was conducted by forming a head substrate 78 in which a curved concave portion 77 was formed so as to be continuous with the same. It was confirmed that the thermal head (not shown) can be made small enough to be brought close to it and can be made smaller and lighter.

Although it has been confirmed that the glass glaze layer 50 can be prevented from rising at the boundary between the flat surfaces 45 and 47 by forming the above-described recess 49 or the like in the head substrate 42, the flat surfaces 45 and 47. It was found that in the recesses 49 and 75 that form an edge at the boundary with, foaming is likely to occur in the glass glaze layer 50 at this position. However, plane 4
It was also confirmed that in the recesses 77 formed continuously in 5, 5 and 47, it was confirmed that foaming was unlikely to occur in the glass glaze layer 50. Therefore, when forming recesses having an angular shape, the edges were formed into a rounded shape. It is desirable to do.

The head substrate 42 of the thermal head 41 of this embodiment has a high flat surface 4 on which the heating resistor 51 is located.
Although it has been illustrated that the minute low plane 46 and the extremely low plane 47 are formed through the inclined planes 44 and 45 and the concave portions 48 and 49 on both sides of 3, the present invention is not limited to the above structure. 6B. Instead, as illustrated in FIG. 6A, a head substrate 83 in which a low flat surface 82 is formed via a flat surface 80 inclined only on one side of the high flat surface 79 and a concave portion 81, and in FIG. Thus, only one inclined plane 85 is formed on one of the high planes 84 and another inclined plane 86 is formed on the other side.
A head substrate 89 having a low flat surface 88 formed through the recesses 87 and a high flat surface 90 as illustrated in FIG.
Head substrate 9 in which flat surfaces 91, 92 inclined to both sides of the recesses, recesses 93, 94 and low flat surfaces 95, 96 are symmetrically formed.
7 and the like are also possible.

Further, in addition to the thermal printer 57 shown in FIG. 2, the present applicant also prototypes a thermal printer 99 having an L-shaped heat dissipation plate 98 elongated in the sub-scanning direction as shown in FIG. Then, an image was actually printed on the recording medium 14 and the characteristics of the thermal head 41 were investigated.
Then, even if the thickness of the glass glaze layer 50 is different from 60 to 100 (μm), there is no great difference in the printing characteristics, but it is confirmed that the smaller the thickness of the glass glaze layer 50 is, the better the rising of the printing density is. Was done.

Here, in this thermal head 41, the glass glaze layer 50 on the flat surface 43 on which the heat generating resistor 51 is located is curved in an arc shape due to surface tension or the like. It is considered that when the width in the sub-scanning direction is different, the width changes to affect print quality. Therefore, the applicant has set the width of the plane 43 in the sub-scanning direction to 10.0, 5.0, 3.0, 2.
Glass glaze layer 50 as 0, 1.5, 1.0, 0.5 (mm)
Head 41 with film thickness of 60, 80, 100, 150
As a comparative object, a thermal head (not shown) having a flat surface and a thermal head (not shown) having a glass glaze layer formed only on a high flat surface were manufactured, and their print qualities were compared. . Therefore, the results of this comparison are illustrated in Table 6 below.

[0063]

[Table 6]

As is clear from the above table, it has been confirmed that the print quality is improved by reducing the width of the flat surface 43 in the sub-scanning direction regardless of the film thickness of the glass glaze layer 50.

As shown in FIGS. 3B and 8A, in this embodiment, the laser scribing recesses 73 and 74 are formed in the mass production substrate 72 in the form of small circular grooves. However, as shown in FIG. 8B, a mass-produced substrate 102 in which a large-diameter circular groove-shaped recess 101 is formed, or as illustrated in FIG. 8C, an isosceles triangular recess 103 is illustrated.
Mass-produced substrate 104 on which is formed, or mass-produced substrate 1 on which a right-angled triangular concave portion 105 is formed as illustrated in FIG.
06 or a rectangular recess 1 as illustrated in FIG.
A mass-produced substrate 108 on which 07 is formed can also be implemented.
However, in the mass-produced substrates 104 and 106 having the triangular recesses 103 and 105, if the laser light is displaced from the center, a processing defect is likely to occur.
3,74 were formed in the shape of a round groove having a small diameter.

[0066]

As described above, according to the present invention, the high surface on which the heating resistor is located and the low surface to which the wiring material is connected are formed on the head substrate, and the inclined surface is continuous with the high surface of the head substrate. By forming the concave portion at the boundary between the inclined surface and the lower surface, it is possible to prevent the thick film or the like formed on the surface of the head substrate from rising at the boundary between the inclined surface and the lower surface. This has an effect such that it is possible to obtain a thermal head in which a wiring material can be satisfactorily connected to the electrodes in the vicinity of the boundary.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a thermal head according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing a thermal printer.

FIG. 3 shows a mass-produced substrate of a head substrate, (a) is a plan view and (b) is a side view.

FIG. 4 is a vertical cross-sectional side view showing an enlarged concave portion of the thermal head.

FIG. 5 is a vertical cross-sectional side view showing a modified example of the concave portion of the thermal head.

FIG. 6 is a side view showing a modified example of the head substrate of the thermal head.

FIG. 7 is a vertical sectional side view showing a modified example of the thermal printer.

FIG. 8 is a side view showing various modified examples of the concave portion of the mass-produced substrate.

FIG. 9 is a perspective view showing a first conventional example.

FIG. 10 is a vertical sectional side view.

FIG. 11 is a perspective view showing a second conventional example.

FIG. 12 is a vertical sectional side view showing a thermal printer of Japanese Patent Application No. 4-67994 proposed by the present applicant.

[Explanation of symbols]

14
Recording medium 41
Thermal head 42,76,78,83,89,97
Head substrate 43 to 47, 79, 80, 82, 84 to 86, 88, 9
0-92,95,96 surface 48,49,75,77,81,87,93,94
Recess 51
Heating resistor 52,53
Electrode 65
Wiring material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Kushida 6-78 Minamimachi, Mishima City, Shizuoka Prefecture, Tokyo Institute of Technology Research Institute

Claims (1)

[Claims] 1. A thermal head in which a large number of heating resistors are continuously arranged on the surface of a head substrate in the main scanning direction, and wiring members are connected to electrodes integrally formed on each of these heating resistors in the sub scanning direction. In, a high surface on which the heating resistor is located and a low surface to which the wiring member is connected are formed on the head substrate, and a boundary between the inclined surface continuous to the high surface of the head substrate and the low surface is formed. A thermal head having a concave portion formed in.